Electron-discharge device



1,640,462 Allg- 1927? R c. MATHES ELECTRON DISCHARGE DEVICE Filed Oct. 1 1924 27 T W /Z I 32 /7 (6 25 35? Patented Aug. 30, 1927.

UNITED STATES 1,640,462 PATENT OFFICE.

ROBERT C. MATHES, OF WYOMING, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A. CORPORATION OF NEW YORK.

ELECTRON-DISCHARGE DEVICE.

Application filed. October 16, 1924. Serial No. 743,903.

This invention relates to electron discharge devices and has for an object a unitary ''device of this character capable of operating as a symmetrical amplifier or re- 5 peater of electric waves without distortion.

To obtain the maximum degree of'amplification of electric waves it is necessary to amplify both halves of the wave cycle, thereb which is substantially free from distortion. This condition is obtainable by using two electron discharge devices, of the threeelement type, in push'pull relation, that is, by connecting the two devices between the divided input and output circuits of an amplifier, as is shown in E. H. Colpitts Patent No. 1,128,292, issued February 16, 1915 and entitled Electric wave amplifier. However, attempts to obtain the same result with a unitary device having a filamentary cathode, two grids disposed on opposite sides of th'e'cathode and two plate electrodes spaced from the grids and connected in a circuit in the same manner as the two separate devices, have not proved satisfactory, since the opposing grids have a tendency-to annul the action of each other at the cathode surface. In accordance with this invention this objectionable feature is overcome by provid ;-:u ing a unitary devicehaving a cylindrical cathode of large surface area, around which are supported two semi-circular grids and -plate electrodes. A pair of shields may be interposed between the'ends of the grids and plates to prevent any annulling eflect at these. points. This arrangement prevents the interacting effect of the opposing grid surfaces, since the cylindricalcathode provides efficient shielding means for a substantially large surface of the opposing electrodes.

Referring to the drawings Fig. 1 shows an electron discharge device with a part broken away to illustrate the arrangement of the electrodes Fig. 2 is a plan view of Fig. 1 to show the space relation of the electrodes; and

Fig. 3 is a diagrammatic view embodying this invention.

provided with an inwardly projecting stem 11. A pair of rods 12 are sealed in the end of the stem 11 and extend longitudinally of the tube, their 'ends being seated in a square block 13'of insulating materiah preferably obtaining a symmetrical wave :o-utput,

The enclosing vessel 10 of the device is of material commercially known "as lavite. A rod 14 is also sealed in the stem midway between the rods 12 and extends through the block 13, its free end being slidable in the block. Supported on the rod 14 is .acylmdrical cathode unit, such as is described andclaimed in M. J. Kelly, application Serial No. 724,754, filed July 8, 1924, entitled Electron discharge devices, and consists of a molded insulating spool 15, rigidly supported on the rod 14 and carrying a heatmg 0011, preferably of tungsten wire. Surrounding the spool 15 and supported thereby is a metallic cylinder 16, preferably of nickel, which is coated with thermionically active material. Alternating current may be supplied to the heating element to activate the cathode 16 without introducing any disturbances in the operation of the device, slnce there is no current flow in the cathode itself. Due. to this arrangement, the cathode 16 is at the same potential throughout its length and the voltage drop between it and the anodes is uniform.

- A pair of semi-circular grids 17 and 18 surround the cylindrical cathode 16 and com prise a number ofsemi-circular wires equally spaced apart and attached at their ends to metallic rods 19 and 20, preferably by spot welding. A supporting r0d-21 is attached to the wires intermediate the ends thereof. The two semi-circular grids are supported from the stem 11 by wires, and the rods 21 are. slidably supported in the insulating block 13, thereby maintaining the proper space relation of the grids 17 and 18 with respect to the cathode 16, while allowing the expansion and contraction thereof. A pair of semi-circular plateelectrodes 22 and 23, preferably of nickel, surround the grid electrodes and are supported from the rods 12 by means of arms 24. Suitable leads are attached t0 the electrodes and are sealed in the stem of the vessel.

Due to the large surface area of the cathode, the opposing grids are prevented from annulling the action of each other to a substantial degree. However, it may be preferable to shield the ends of the grids since there may be some interaction of the opposing ends. This may be accomplished by providing a pair of metallic shields 25 and 26, which are supported from the stem 11 by rods 27 and 28, the upper ends of the shields being slidablysupported in the insulating lUU block 13 by means of rods 29 and 30. These shields are connected to the cathode by means of wires 31, whereby the shields are always at the same potential as the cathode. By virtue of the geometric arrangement of the electrodes and the largeactive cathode surface and the completely shielded opposing surfaces of theielectrodes, the impedance of this device is very low and its space current correspondingly high. As a result, the amplification factor can be made much higher for the same output impedance than electron discharge devices of corresponding size having filamentary cathodes, and due to the complete shielding means between the opposing grids and plate electrodes, no interacting effeet is possible, thereby securing a high degree of amplification in the output circuit which is substantially free from distortion. A device of this character may be used to efficiently produce a perfect form reproduction of the electric wave received in the input circuit, and may be used as a repeater or amplifier of electric waves. In Fig. 3 this invention is adapted to an amplifier circuit in which the two grids 17 and 18 are connected to the ends of the secondary winding of the input transformer 32. The two plates 22 and 23 are connected to the primary winding of the output transformer 33. The cylindrical cathode 16 is connected to the input circuit through battery 34 conductor 35 and grid battery 36 connected to the midpoint of the secondary winding of transformer 32, and connected to the output circuit through battery 37 and conductor 38 to the midpoint of the primary winding of transformer 33. The device of this invention connected in an amplifier in such a way, will efliciently amplify an incoming wave without distortion and also prevent the interaction of the opposing electrode surfaces. The invention. may also be utilized to rectify both halves of an alternating current wave by any convenient circuit arrangement. Furthermore, the grids may be removed and the device operated as a double rectifier.

Although this invention has been described with reference to a particular arrangement, it is, of course, understood that various modifications may be made in the detailed struc ture without departing from the scope of the invention as defined in the appended claims.

What is claimed is: 1. An electron discharge device comprising a vessel having a press, a plurality of concentric hollow semi-cylindrical electrodes supported from said press, and shielding means disposed between the ends of two of said electrodes.

2. An electron discharge device comprising a vessel having a press, a plurality of concentric hollow semi-cylindrical electrodes supported from said press, and a pair of shields insulatingly supported from said press and being adjacent the ends of said electrodes.

3. An electron discharge device comprising a vessel having a press, a plurality of concentric hollow semi-cylindrical electrodes supported from said press, a cylindrical cathode coaxial with cylindrical electrodes, and a pair of shields insulatingly supported from said press, said shields being in an axial plane of said cathode.

4. An electron discharge device-comprising a vessel having a press, a plurality of hollow semi-cylindrical electrodes insulatingly supported from said press, a cylindrical cathode concentric with said electrodes, and means connected to said cathode to prevent the annulling efl'ect of said electrodes.

5. An electron discharge device con'iprising a vessel having a press, supporting rods sealed in said press, an insulating member carried by said rods,.a plurality of hollow semi-cylindrical electrodes supported between said prcss and insulating member, and a pair of shields dividing said electrodes and -.being supported from said insulating memher.

6. An electron discharge device co1npris ing a vessel having a press, a pair of rods supported from said press, an insulating member supported from said rods and supporting a plurality of concentric electrodes, and shielding means slidably guided by .said insulating member.

7. An electron discharge device comprising a plurality of hollow semi-cylindrical electrodes, a cylindrical cathode axially arranged with respect to said electrodes, and a shield connected to said cathode and slidably guided between said hollow semi-cylindrical electrodes.

In witness whereof, I hereunto subscribe my name this 10th day of October, A. D.

ROBERT C. MATHES.

said hollow semi-' il U 

